In general, the processing of a silver halide color photographic material consists of steps of color development and desilvering. Silver which has been produced in the development step is then oxidized with a bleaching agent and dissolved with a fixing agent. As bleaching agent there may be mainly used a, ferric complex salt, e.g., aminopolycarboxylic acid-ferric complex salt. As fixing agent there may be normally used a thiosulfate.
On the other hand, the processing of a black-and-white photographic light-sensitive material consists of steps of development and removal of unexposed silver halide. Unlike the processing of a color photographic light-sensitive material, the black-and-white photographic light-sensitive material which has been developed is then fixed without being bleached. In this case, too, as fixing agent there is normally used a thiosulfate.
It has been desired to speed up both the color development and the black-and-white development. It has thus been studied to shorten each processing step. This doesn't except the fixing step. Various fixing accelerators have been studied. Little or no effective fixing accelerators have been found. It is possible to use fixing agents other than thiosulfates to-speed up the fixing step.
Examples of fixing agents to replace thiosulfates include 1,2,4-triazolium-3-thiolates of mesoionic compounds as described in U.S. Pat. No. 4,378,424, and JP-A-57-150842 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). However, no full studies have been made on these fixing agents.
JP-A-1-201659 discloses the use of mesoionic compounds as bleach accelerators in the bleaching bath or blix bath. Further, JP-A-2-44355 discloses the use of 1,2,4-triazolium-3-thiolate compounds as fixing accelerators in the fixing bath. However, the above cited patents give no reference to the effects of the present invention.
Other examples of mesoionic compounds include those disclosed in U.S. Pat. Nos. 4,003,910, 4,675,276, 4,624,913, and 4,631,253, and JP-A-62-217237, JP-A-64-3641, JP-A-60-144737, JP-A-62-253161, JP-A-62-287239, JP-A-61-176920, JP-A-62-96423, and JP-A-1-154056. However, all these mesoionic compounds are intended to be incorporated in the photographic light-sensitive material or the developer. The above cited patents give no reference to the effects of the present invention.
There is an increasing demand for the improvement in the image preservability. For this purpose, studies have been made on both the material to be used in the light-sensitive material and the final processing bath. However, these approaches still leave much to be desired. Thus, there have been not yet attained desired desilvering properties and image preservability. It has thus been desired to drastically improve these properties.
Further, the above mentioned bleaching agent and fixing agent are used in the same bath as blix bath in the processing of a color photographic paper, etc., for the purpose of speeding up the processing. The bleaching agent to be used in the blix bath is normally an ethylenediaminetetraacetic acid-ferric complex salt. It is the recent tendency that an oxidizing agent having a higher oxidizing power (high redox potential) is used in the bleaching bath to further speed up the processing. However, it has been known that such an oxidizing agent causes significant bleach fogging or that if used as blix bath, it causes a problem of solution stability or the like. The solution stability problem is that the thiosulfate is deteriorated by oxidation and then precipitated.
In recent years, this problem has become more remarkable as the replenishment rate decreases. In order to inhibit the oxidation of thiosulates, sulfites are normally used as preservatives. However, if sulfites are used in a large amount, they are oxidized to cause precipitation of Glauber's salt or other problems. Thus, it is difficult to use sulfites as a countermeasure.
On the other hand, U.S. Pat. No. 4,378,424, and JP-A-57-150842 disclose that as fixing agents to replace thiosulfates there may be used mesoionic compounds. However, the above cited patents give no reference to the effects in the blix bath as stated herein.
Moreover, JP-A-2-44355 discloses the incorporation of 1,2,4-triazolium-3-thiolate compounds as fixing accelerators in the fixing bath. JP-A-1-201659 discloses the incorporation of mesoionic compounds as bleach accelerators in the bleach or blix bath. However, the above cited patents give reference neither to the use of mesoionic compounds as fixing agents in the blix bath nor to the effects of the present invention.
If these mesoionic compounds are used as accelerators, they often work well in a small amount. These mesoionic compounds serve to remove substances which are adsorbed by silver halide (or silver). Thus, these approaches greatly differ in the amount of mesoinic compounds to be used and their functions from the present invention, in which mesoionic compounds are used as fixing agents. Therefore, the present invention cannot be easily worked out from the above cited patents.
Further examples of mesoionic compounds are disclosed in U.S. Pat. Nos. 4,003,910, 4,675,276, 4,624,913, and 4,631,253, and JP-A-62-217237, JP-A-64-3641, JP-A-60-144737, JP-A-62-253161, JP-A-62-287239, JP-A-61-176920, JP-A-62-96943, and JP-A-1-154056. However, all these mesoionic compounds are intended to be incorporated in the photographic light-sensitive material or the developer. The above cited patents give no reference to the effects of the present invention.
Thus, it can be said that there have been not yet found a blix bath that can eliminate both the bleach fogging problem and the solution stability problem at the same time.